package com.singzi.leetcode.N1100;

/**
 * 给定一个包含n 个整数的数组nums和一个目标值target，判断nums中是否存在四个元素 a，b，c和 d，使得a + b + c + d的值与target相等？
 * 找出所有满足条件且不重复的四元组。
 *
 * 来源：力扣（LeetCode）
 * 链接：https://leetcode-cn.com/problems/4sum
 *
 */

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class T1018 {
    public static void main(String[] args) {
        Solution18 test = new Solution18();
        int []a = {2,2,-2,-2,0,0,1,1,-1,1,1,0,0,0,0,0,1};
        System.out.println(test.fourSum(a, 0));

    }
}


class Solution18{
    public List<List<Integer>> fourSum(int[] nums, int target){
        List<List<Integer>>list = new ArrayList<List<Integer>>();
        if(nums.length <4||nums==null){
            return list;
        }
        Arrays.sort(nums);
        int length = nums.length;

        for (int i = 0; i < length-3; i++) {
            if(i>0&&nums[i]==nums[i-1]){
                continue;
            }
            if(nums[i]+nums[i+1]+nums[i+2]+nums[i+3]>target){
                break;
            }
            if(nums[i]+nums[length-3]+nums[length-2]+nums[length-1]<target){
                continue;
            }
            for(int j=i+1;j<length-2;j++){
                if(j>i+1&&nums[j]==nums[j-1]){
                    continue;
                }
                if(nums[i]+nums[j]+nums[j+1]+nums[j+2]>target){
                    break;
                }
                if(nums[i]+nums[j]+nums[length-2]+nums[length-1]<target){
                    continue;
                }
                int left = j+1;
                int right = length-1;
                while(left<right){
                    int sum = nums[i]+nums[j]+nums[left]+nums[right];
                    if(sum==target) {
                        list.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
                        while (left < right && nums[left] == nums[left + 1]) {
                            left++;
                        }
                        left++;
                        while (left < right && nums[right] == nums[right - 1]) {
                            right--;
                        }
                        right--;
                    }else if(sum<target) {
                        left++;
                    }else{
                        right--;
                    }
                }


            }

        }
        return list;




        }

}
